> I haven't a clue about this "n-key rollover" thing.  I only own
> [...].  None of them have key repeat problems.

"repeat" != "rollover".

> Is this a USB ailment?

Perhaps.  More likely it's a cheap-keyboard ailment.

N-key rollover essentially means that regardless of what keys you have
pressed, another keypress will be correctly registered.  Simple matrix
keyboards can't do it; a matrix keyboard with a diode added to each
switch will.

It has nothing to do with repeat.

I once had the (mis)fortune to use an iMac with a USB keyboard.  I'm a
pretty fast typist, and while I don't really depend on full-blown N-key
rollover, I need a decent approximation, or my error rate goes through
the roof.  This keyboard Just Didn't Cut It.  I remember that whenever
I typed "netbsd", unless I deliberately throttled back on my keystroke
speed, I would regularly get the last keystroke or two effectively
turned into deletes.

I don't know if this is a USB thing, a Mac thing, an Apple thing, or
just that that particular keyboard design had had corners cut.

/~\ The ASCII				der Mouse
\ / Ribbon Campaign
 X  Against HTML	       mouse@rodents.montreal.qc.ca
/ \ Email!	     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B